CHM103 Chapter 1_2 noR (2)

Chapter 1: Matter, Measurements, and Calculations

ATOMS AS THE BASIS OF MATTER

Democritus (460-370 BC)

  • First person to suggest that atoms are the basis of matter.

  • The term ‘atoms’ comes from the Greek word 'atomos', meaning "no cut".

  • Proposed the existence of different types of atoms.

  • Introduced concept of matter composed of atoms and void space.

  • Aristotle (384-322 BC) opposed the atomic theory, arguing against the existence of a void, which led to the theory being neglected for about 1500 years.

John Dalton (1766-1844)

  • Known as the Father of Modern Atomic Theory.

  • Established theories based on experimental evidence with gases.

DALTON'S ATOMIC MODEL OF MATTER

  • All matter consists of tiny particles called atoms.

  • Atoms of unique types are classified as elements.

  • Collections of bonded atoms are termed molecules.

  • The term 'compound' encompasses molecules, atoms, and ions (atoms with an abnormal electron count).

  • Compounds exhibit a fixed ratio of atoms.

  • Chemical reactions do not create or destroy atoms; they only rearrange them and can change the compounds.

BALANCED CHEMICAL EQUATIONS

  • A balanced chemical equation reflects Dalton’s laws:

    • All matter is made of elements.

    • Different elements consist of different atoms.

    • Atoms combine to form compounds.

    • Atoms are conserved and merely recombined during chemical reactions.

  • Example: N2 + 3H2 ➜ 2NH3

TYPES OF MOLECULES

Diatomic Molecules

  • Comprise two bonded atoms.

  • Examples: O2 (oxygen gas) and CO (carbon monoxide).

Triatomic Molecules

  • Consist of three bonded atoms.

  • Examples: CO2 (carbon dioxide) and H2O (water).

Polyatomic Molecules

  • Composed of four or more bonded atoms.

  • Examples: HNO3 (nitric acid) and C6H12O6 (glucose).

  • All foods (e.g., proteins, oils, starches) are polyatomic molecules.

Homoatomic Molecules

  • Contain identical atoms.

  • Example: H2 (hydrogen gas), S8 (sulfur).

Heteroatomic Molecules

  • Feature two or more different atoms.

CLASSIFICATION OF MATTER

Pure Substances

  • Defined as having a constant composition and fixed physical/chemical properties.

  • Example: Pure water consistently maintains the same hydrogen and oxygen proportions and has a specific freezing temperature.

Heterogeneous Mixtures

  • Properties depend on the sampling location.

  • Examples: pizza pie (crust vs. pepperoni) and chicken noodle soup (noodles vs. broth).

Elements

  • Pure substances formed from either homoatomic molecules or individual atoms.

  • Examples: O2 (oxygen gas) and copper metal (individual copper atoms).

Compounds

  • Pure substances made from atoms of different kinds forming heteroatomic molecules or ions.

  • Examples: H2O (water) and NaCl (table salt).

  • Ionic compounds don’t count as molecules.

MATTER CLASSIFICATION SUMMARY

  • Mixture: Heterogeneous, Homogeneous

  • Pure Substance: Element, Compound

  • Examples: Fruit salad, gasoline, water.

HOMOGENEOUS MIXTURES

  • Also known as solutions; properties are consistent throughout the mixture.

  • Example: NaCl mixed with water has uniform taste regardless of sampling location.

  • Characterized as mono-phasic.

TYPES OF SOLUTIONS

  • Liquid/Solid: Water + NaCl -> seawater.

  • Gas/Gas: N2 + CO2/O2/NO2/SO2 -> atmosphere.

  • Solid/Solid: Au + Ag -> jewelry (amalgam).

  • Liquid/Liquid: Different proportions of H2O and ethanol -> various types of vodka.

TRUE STATEMENTS ABOUT HOMOGENEOUS SOLUTIONS

  • Homogeneous solutions contain one solvent and are monophasic.

MEASUREMENTS AND MEASUREMENT UNITS

  • Measurements consist of a number and a unit (e.g., feet, pounds).

  • Units are standardized by agreement.

  • Measuring devices include rulers, balances, graduated cylinders.

THE METRIC SYSTEM OF MEASUREMENT

  • A decimal system where units relate by factors of 10.

  • The meter was initially defined as 1/10,000,000 of the distance from the North Pole to the equator.

MEASUREMENT UNITS

Basic vs. Derived Units

  • Basic units (e.g., 1 meter) used to calculate derived units (e.g., 1 m²).

The Kilogram

  • Standardized in 1879, initially made of platinum and iridium, known as the Kilogram of Le Grand K.

DECIMAL TIME

  • Attempted introduction with 10 hours a day, but reverted to the 24-hour system due to public dislike.

USE OF PREFIXES

  • Prefixes enhance understanding by relating basic and derived units.

TRUE STATEMENTS ABOUT MEASUREMENTS

  • For example, 5 kg = 5000 g and 10,000 ml = 10 L.